not sure if this has been posted previously, in May the Horse magazine (Bloodhorse counterpart) put out a special section about the diease. It's really a big Phizer advertisement but contains good information for anyone who doesn't know what Equine herpersvirus is or does...
http://www.thehorse.com/pdf/ehv/specialreport.pdf
I also saw a report from Cornell last year that said one of their researchers had discovered that horses vaccinated with a modified live virus (MLV) fared much better when exposed than horses vaccinated with the standard killed virus...thus far I believe this is only in the research stages, I think that most horses right now are given a killed version of the vaccine.